At the annual review of PEPS project (CNES Sentinel global mirror site), the GEOSYS company showed its operational activities centered on the use of Sentinel-2 data to provide advise on agriculture on many regions of the world. On this occasion, GEOSYS showed their cloud detection process for Sentinel-2 images. The Sen2cor solution was not considered reliable enough y GEOSYS, and the regions processed by MACCS within MUSCATE are far from covering all the regions of interest of the company. GEOSYS decided to rely on human operators to improve the cloud masking. For each processed Sentinel-2 image, a man made valid pixel mask is build ("valid" means without clouds and cloud shadows).

After France, Belgium, North of Spain, Tunisia, a transect from Burkina Faso to Mali and some tiles in Ethiopia, Theia just released the production of one year of Sentinel-2A data at Level 2A above a large region of Morocco, from Ouarzazate to Casablanca. Level 2A products provide surface reflectances corrected from atmospheric effects, with a high quality cloud mask.

The L2A data are, as always, available from https://theia.cnes.fr. Please refer to the help page to find the data format description. To download the data without a click, you may use our python download tool (after having registered on Theia's site).

V1_0 was a preliminary processing performed with early version of MACCS adapted to Sentinel-2. It was plagued with a bug in the cloud shadow mask : when more than 255 clouds were present in one image, shadow detection went completely wrong and shadows were detected anywhere. V1_0 was not produced in MUSCATE operationnal context, but in an earlier validation context. Production was available over France only.

V1_1 replaces V1_0 over France, Production started mid November, but was only released in February because of many difficulties encountered by MUSCATE. It corrects for the bug related to cloud shadows observed with V1_0, and was fully processed by the operational MUSCATE center.

V1_2 was used in another context not related to MUSCATE, you will not find any product with this version number within MUSCATE server.

V1_3 was applied starting from February 2017, to data sets produced above Reunion, Burkina, Senegal, Tunisia, Morocco.The aerosol estimate is improved compared to V1_1. Together with Bastien Rouquié, from CESBIO, we worked on the tuning of the blue-red ratio which is used in the multi-spectral method to estimate aerosols (which is combined with a multi-temporal method). Initially, we used bands B2 (Blue) and B4 (Red), with a ratio of 0.45. We found out that better results were obtained with B1 (Blue) and B4 (Red), still with a ratio of 0.45. More accurate studies tend to recommend a higher value, closer to 0.5

As can be seen in the figure below, the estimates obtained with V1_3 are not biased anymore, and have a reduced standard deviation. As a consequence of getting a lower aerosol optical thickness, the surface reflectances of V1_3 products are 2% higher than those of the earlier versions (some user feedbacks from V1_0 said reflectances were sometimes too low).

Using B2/B4 ratio

Using B1/B4 ratio

V1_4 will be provided with a better shadows mask, as it has been found that the shadows masks are too severe and contain too many commission errors. It is in its final stages of validation.

After having repeated month after month " sorry, our L2A product production is late again for this ou that reason" in this blog, on the phone, during meetings, via email or on social networks, you can't imagine my pleasure to announce that CNES just released large time series of Sentinel-2A L2A data, over France, Reunion Island, North of Spain, Belgium, Luxembourg, and on some large sites in Burkina Faso, Mali, Ethiopia, and Tunisia. We process one whole year of data from December 1st 2015 to December 1st 2016. More than 5000 tiles where just released. Processing over Tunisia goes on and Morocco and Senegal are next on the list. Then, we will process Madagascar, and the all the zones displayed here. The data were processed using the MACCS processor.

Since the new CNES cluster has been installed, the MUSCATE production rate has been steady, around 100 products per day. This is not full speed, as MUSCATE still needs a few updates to be more robust and can't still be used at full capacity, and as the CNES cluster is in its tuning phase and is often running quite slow. However, the production of all data above France, Belgium, and North of Spain (Pyrenees, Ebro basin, Catalonia) should be completed this week-end and pushed to the distribution server next week. The new products will have version number V1_1. This version brings mainly a few bug corrections, regarding the cloud shadows for instance.

Then we will proceed with 3 other zones ; Burkina, Morocco and Tunisia. To start real time production, we are waiting for the end of validation of the adaptation to the new format of Sentinel-2 data, which started to be used of the 4th of December 2017. It's nearly ready !

Because of the little issues we stumbled upon when producing Sentinel-2 level 2A data over France with MUSCATE, we had not yet demonstrated an end-to-end production, with a distribution on the operational server. While waiting for the end of the production of data over metropolitan France, we did this test the processing of Réunion Island.

September 2016 eruption witnessed by Sentinel-2A

The island is covered by only one Sentinel-2 tile, but the processing worked very smoothly, which is a very good sign after all teh difficulties we met. The data are now released on :

We processed all the available data, strating from January the 18th, 2016, until end of November. To produce the data acquired later on, we are waiting for the new version of PEPS, compatible with the new Sentinel-2 data format. We hope it will be possible as soon as February. .
The data set includes a nice image of the eruption of the Piton de la Fournaise volcano, in September. Regarding the data quality, you may find that the cloud shadows are a little exaggerated. We will try to fix that with a better tuning of the threshold for the next versions.